Optimization of solid-phase microextraction conditions using a response surface methodology to determine organochlorine pesticides in water by gas chromatography and electron-capture detection

A response surface methodology was applied to optimise the solid-phase micr oextraction (SPME) conditions using a polyacrylate-coated fiber to determin e thirteen organochlorine pesticides from water. Analyses were performed us ing gas chromatography-electron-capture detection. Variables affecting abso rption in both the headspace and immersion extraction were optimised by usi ng a response surface generated with a Doehlert design, and the results wer e compared. The immersion SPME method was selected since higher recoveries were obtained for most of the compounds studied. The method developed was a pplied to the analysis of tap and Ebro river water samples. The linear rang e of most pesticides for real samples was found to be between 0.001 and 2.5 mu g l(-1) and the limits of detection were between 0.15 and 0.35 ng l(-1) . The repeatability and the reproducibility between days of the method (n=6 ), expressed as relative standard deviation, for tap water spiked at a leve l of 1 ng l(-1) were between 5.7 and 25.6% and between 7.6 and 26.5%, respe ctively. (C) 1999 Elsevier Science B.V. All rights reserved.